Responses
Uh I think you don't know what grooming is. Suoh is already an adult at that part and even when Suoh's a child Nio hadn't had any sexual thought towards him. Nio did nothing besides providing Suoh as a guardian normally, what grooming is there. And the one who made the first sexual move was grown-up Suoh. There's no grooming or pedophilia here.

http://www.mangago.zone/read-manga/koisuru_alpha_no_sodatekata/uu/ibx_chapter-2/pg-14/
so basically... grooming?